linux-kernel - Re: [PATCH 1/3] of: base: add support to get machine compatible string

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <2a644b8c-d91e-5ab1-200b-00f749a36307@arm.com>
Date:   Wed, 23 Nov 2016 10:05:24 +0000
From:   Sudeep Holla <sudeep.holla@....com>
To:     Sekhar Nori <nsekhar@...com>
Cc:     Bartosz Golaszewski <bgolaszewski@...libre.com>,
        Kevin Hilman <khilman@...libre.com>,
        Michael Turquette <mturquette@...libre.com>,
        Rob Herring <robh+dt@...nel.org>,
        Frank Rowand <frowand.list@...il.com>,
        Mark Rutland <mark.rutland@....com>,
        Peter Ujfalusi <peter.ujfalusi@...com>,
        Russell King <linux@...linux.org.uk>,
        Sudeep Holla <sudeep.holla@....com>,
        LKML <linux-kernel@...r.kernel.org>,
        arm-soc <linux-arm-kernel@...ts.infradead.org>,
        linux-drm <dri-devel@...ts.freedesktop.org>,
        linux-devicetree <devicetree@...r.kernel.org>,
        Jyri Sarha <jsarha@...com>,
        Tomi Valkeinen <tomi.valkeinen@...com>,
        David Airlie <airlied@...ux.ie>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Robin Murphy <robin.murphy@....com>
Subject: Re: [PATCH 1/3] of: base: add support to get machine compatible
 string



On 23/11/16 07:49, Sekhar Nori wrote:
> On Tuesday 22 November 2016 09:16 PM, Sudeep Holla wrote:
>> Hi Sekhar,
>>
>> On 22/11/16 15:06, Sekhar Nori wrote:
>>> Hi Sudeep,
>>>
>>> On Tuesday 22 November 2016 04:23 PM, Sudeep Holla wrote:
>>>>
>>>>
>>>> On 22/11/16 10:41, Bartosz Golaszewski wrote:
>>>>> Add a function allowing to retrieve the compatible string of the root
>>>>> node of the device tree.
>>>>>
>>>>
>>>> Rob has queued [1] and it's in -next today. You can reuse that if you
>>>> are planning to target this for v4.11 or just use open coding in your
>>>> driver for v4.10 and target this move for v4.11 to avoid cross tree
>>>> dependencies as I already mentioned in your previous thread.
>>>
>>> I dont have your original patch in my mailbox, but I wonder if
>>> returning a pointer to property string for a node whose reference has
>>> already been released is safe to do? Probably not an issue for the root
>>> node, but still feels counter-intuitive.
>>>
>>
>> I am not sure if I understand the issue here. Are you referring a case
>> where of_root is freed ?
>
> Yes, right, thats what I was hinting at. Since you are giving up the
> reference to the device node before the function returns, the user can
> be left with a dangling reference.
>

Yes I agree.

>> Also I have seen drivers today just using this pointer directly, but
>> it's better to copy the string(I just saw this done in one case)
>
> Hmm, the reference is given up before the API returns, so I doubt
> copying it later is any additional benefit.
>

True.

> I suspect this is a theoretical issue though since root device node is
> probably never freed.
>

Indeed, not sure if it's worth adding additional code to release the nod
at all call sites.

-- 
Regards,
Sudeep